Apparatus and method for mounting component

ABSTRACT

A component mounting system includes first to third (pickup, transfer, and placement) stations. A component supplied at the component supply is picked up by a transport head at the pickup station and then transferred to a placement head at the transfer station. The placement head carries the component to the placement station where the component is placed and mounted on a substrate such as circuit board. The component held by the placement head is recognized by an imaging device at or in the vicinity of the transfer station.

TECHNICAL FIELD OF THE INVENTION

[0001] The present invention relates to an apparatus and method formounting components such as electric devices on a substrate or circuitboard.

BACKGROUND OF THE INVENTION

[0002] Generally, a component mounting apparatus has been used widelyfor a sequential positioning or mounting of electric components on asubstrate such as printed circuit board. FIG. 12 shows a conventionalcomponent mounting system. The system generally indicated by referencenumeral 100 includes a component supply 110 for supplying components; atransport head 120 for picking up one of the components from thecomponent supply 110 and then turning the component upside down toorient the component in a predetermined mounting direction; a placementhead 130 for receiving the component from the transport head 120 andthen placing the component onto the substrate or printed circuit boardin place; an imaging camera 140 for capturing an image of the componentreceived by the placement head 130; a holder 150 for holding and thenpositioning the circuit board in place in the system 100; anotherimaging camera 160 for capturing an indication marked on the circuitboard; a controller 170 for controlling the whole operation of thesystem 100. The placement head 130, which is supported to movehorizontally in the X-direction in FIG. 12, is equipped with a vacuumnozzle or quill capable of rotating about a vertical Z-axis.

[0003] Referring to FIGS. 13 and 14 operations of the system will bedescribed hereinafter. In the drawing, the component supply 110 isprovided with a number of components 111 supported and separated fromanother on an expanded plate 112. The components 111 are each recognizedby an imaging device or camera 113. Based upon the recognition, thecontroller 170 moves the component supply 110 so that one component 111a to be mounted in the subsequent mounting is positioned in apredetermined pickup position. The transport head 120 travels to aposition right above the component 111 a, moves downward to contact thecomponent 111 a, and then sucks the component 111 a for unloading. Afterunloading, the transport head 120 moves upward and then travels in theX-direction to a transfer station. At the transfer station, thetransport head 120 together with the component turns upside down asindicated by arrow 121. This brings the component 111 from anupside-down position into an upright position so that one surface (i.e.,bottom surface with solder bumps or electrical connections) to beopposed the circuit board is faced downward. The placement head 130approaches the component 111 a in the upright position from above toreceive the component from the transport head 120. Then, the placementhead 130 moves upward and then travels in the X-direction toward aplacement station. The transport head 120, after being deprived of thecomponent, moves back to the pickup station for the subsequent pickupoperation

[0004] During the operation described above, a circuit board 151 istransported to and then held in position by the holder 150. The imagingdevice or camera 160 approaches the circuit board 151 to capture theindication defined on the circuit board, indicative of a referenceposition for the mounting of the component. The captured image is thentransmitted to the controller 170.

[0005] As best shown in FIG. 13, the imaging device 160 together withanother imaging device 140 is mounted on an optical head 180. After therecognition of the indication on the circuit board 151, the optical head180 moves back in the X-direction toward the placement head 130 that isrunning in the opposite direction. Once opposed, not only the opticalhead 180 but also the placement head 130 comes to a halt. In this state,the component 111 a held by the placement head 130 is recognized by theimaging device 140. The image captured by the imaging device 140 istransmitted to the controller 170. At this moment, the sucking nozzle ofthe placement head 130 for sucking and holding the component 111 a ismaintained in an elevated position. This prevents the nozzle from makinga conflict with the imaging device 140. Also, the sucked component 130is held within a field of the imaging device 140.

[0006] After the completion of the recognition, the placement head 130with the component 111 a restarts travelling in the X-direction againtoward the mounting station. During the travel, the recognition resultsof the component 111 a and the circuit board 151 (in particular, thereference indication) are used for calculations performed in thecontroller 170. The controller 170 calculates the displacement in theX-direction of the placement head 130 for the mounting of the component111 a onto the predetermined position of the circuit board 151. Alsocalculated in the controller 70 are the rotational angle of the nozzleabout the Z-axis and the displacement of the circuit board 151.According to the calculation made by the controller 170, the placementhead 130 travels in the X-direction to a position where it opposes thecircuit board 151. At this moment, the corrections for the nozzle andthe circuit board 151 have already been completed. Then the placementhead 130 causes the nozzle to move downward, so that the component 111 ais mounted in position on the circuit board 151.

[0007] After mounting, the placement head 130 releases the component 111a and then pulls up the nozzle in the Z-direction to a certain level.Then, the imaging head 180 moves in between the circuit board 151 andthe placement head 130 so that the imaging device 160 determines whetherthe component 111 a takes the predetermined position on the circuitboard 151. Another imaging device 140, on the other hand, recognizeswhether the placement head 130, in particular the tip end of the nozzle,carries any debris. Once the recognition has been completed, theplacement head 130 moves back in the X-direction for receiving the nextcomponent. By the repetition of the series of operations describedabove, the components on the expanded panel 112 are mounted sequentiallyon the respective circuit boards with a cycle time of about, forexample, 1.9 seconds.

[0008] However, the conventional component mounting system has severaldrawbacks in the recognition operations. For example, for therecognition of the component, the placement head 130 after it hasreceived the component 111 a is accelerated to a certain velocity.Immediately after the acceleration, the placement head 130 comes to atemporal halt for the recognition of the component 111 a by the imagingdevice 160. This requires further acceleration and deceleration of theplacement head 130 before the actual mounting of the component 111 a.Also, the placement head 130 after it has come to a halt continues tovibrate for a certain period, which requires the imaging camera 160 towait until the termination of the vibration in order to attain theprecise recognition of the component 111 a. This in turn reduces theoperational efficiency of the mounting.

[0009] Further, as shown in FIG. 14, in the operation for therecognition of the circuit board 151, the nozzle 131 of the placementhead 130 is moved upward to the elevated position as indicated by arrow135. Then, as indicated by arrow 145, the optical head 180 moves inbetween the elevated nozzle 131 and the circuit board 151 for imaging bythe imaging devices 140 and 160. A distance between the elevated nozzleand the circuit board, indicated by alphabet H, is designed to be about40 mm, for example, in order to prevent the interference of the opticalhead 180 with the nozzle 131 and also to ensure a proper imagingoperation of the optical head 180. The elevation of the nozzle 131requires 0.1 second even by the use of a high-speed voice coil motor.

[0010] Furthermore, the conventional mounting system is equipped with aninterlock to avoid the interference of the optical head 180 with theplacement head 130 during the recognition operations by the optical head180 before and after the mounting. This complicates the structure of themounting system 100 and makes the system less economical.

[0011] Moreover, the conventional recognition procedure requires theplacement head 130 and the optical head 180 to travel along complicatedpasses, respectively. This in turn requires the mounting system to havea more number of drive shafts and acceleration/deceleration operations,which further reduces the positional precision of the moving part andthereby the imaging quality.

SUMMARY OF THE INVENTION

[0012] Accordingly, an object of the present invention is to provide animproved component mounting apparatus and method.

[0013] To this end, the component mounting apparatus of the presentinvention has a component supply provided at a first station forsupplying a component; a transport head for picking up the component atthe first station from the component supply and then transporting thecomponent to a second station; a placement head for receiving thecomponent from the transport head at the second station and thentransporting the component to a third station; a substrate provided atthe third station, the substrate being provided with the component fromthe placement head at the third station; and an imaging unit forrecognizing the component held by the placement head; wherein the firstimaging unit is positioned in or in the vicinity of the second station.

[0014] Another component mounting apparatus of the present invention hasa component supply provided at a first station for supplying acomponent; a transport head for picking up the component at the firststation from the component supply and then transporting the component toa second station; a placement head for receiving the component from thetransport head at the second station and then transporting the componentto a third station; a substrate holder for holding a substrate, thesubstrate holder being movable between the third station and a fourthstation spaced a certain distance away from the third station; a firstimaging unit for recognizing the component held by the placement head;and a second imaging unit positioned at the fourth station forrecognizing the substrate.

[0015] Another component mounting apparatus of the present invention hasa component supply provided at a first station for supplying acomponent; a transport head for picking up the component at the firststation from the component supply and then transporting the component toa second station; a placement head for receiving the component from thetransport head at the second station and then transporting the componentto a third station; a substrate holder provided at the third station forholding a substrate, the substrate being provided with the componentfrom the placement head at the third station; a first imaging unit forrecognizing the component held by the placement head; and a secondimaging unit for recognizing the substrate; wherein the first and secondimaging units are arranged not to interfere with a passage of theplacement head.

[0016] Also, a component mounting method has picking up a component by atransport head from a component supply at a first station; transportingthe component from the first station to a second station by thetransport head; transferring the component from the transport head to aplacement head at the second station; recognizing the component receivedby the placement head at or in the vicinity of the second station;transporting the component from the second station to a third station bythe placement head; placing the component onto a substrate at the thirdstation by the placement head; and controlling the step of placing thecomponent onto the substrate based upon information obtained by therecognition of the component.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a perspective view of a component mounting apparatusaccording to a preferred embodiment of the present invention;

[0018]FIG. 2 is an exploded perspective view of various elements of thecomponent mounting apparatus in FIG. 1;

[0019]FIG. 3 is a side elevational view showing the movement of elementsin the component mounting apparatus shown in FIG. 1;

[0020]FIGS. 4A through 4I are side elevational views each showing themovement of elements in the component mounting apparatus shown in FIG.1;

[0021]FIGS. 5A and 5B are graphs showing time versus moving velocityrelations of the placement head in the conventional system and thesystem according to the present invention;

[0022]FIG. 6 are graphs showing time versus moving velocity relations ofthe transport and placement heads and the substrate holder together withthe transport pass of the component;

[0023]FIG. 7 is a block diagram of the component mounting apparatusaccording to the preferred embodiment of the present invention;

[0024]FIG. 8 is a perspective view of a component mounting apparatusaccording to another preferred embodiment of the present invention;

[0025]FIGS. 9A through 9K are side elevational views each showing themovement of elements in the component mounting apparatus shown in FIG.8;

[0026]FIGS. 10A and 10B are side elevational views of the imaging deviceand the component in the conventional system and the system according tothe present invention;

[0027]FIGS. 11A through 11F are side elevational views of the componentrecognizing device according to another preferred embodiments of thepresent invention;

[0028]FIG. 12 is a schematic perspective view of the conventionalcomponent mounting apparatus;

[0029]FIG. 13 is an exploded perspective view of various elements of theconventional component mounting apparatus in FIG. 12; and

[0030]FIG. 14 is a side elevational view of the movable elements in theconventional component mounting apparatus in FIG. 12.

PREFERRED EMBODIMENTS OF THE INVENTION

[0031] With reference to the drawings, a variety of embodiments of acomponent mounting system and its method according to the presentinvention will be described in detail hereinafter. It should be notedthat although a vacuum nozzle is used for holding a component and acircuit board is employed for a substrate to which the component ismounted, the present invention is not limited thereto. For example, thevacuum nozzle may be replaced by another mechanical holder or chuck forholding the component by a mechanical engagement with the component.Also, the substrate may be another device or housing to which thecomponent is mounted.

[0032] Referring to FIG. 1, there is shown an embodiment of thecomponent mounting system, generally indicated by reference numeral 1,according to the present invention. Generally, the system 1 has acomponent supply 10 for supplying components to the system 1; atransport head 20 for picking up each component from the componentsupply 10 and then turning upside down to orient the component in adirection along which the component is mounted onto the substrate; aplacement head 30 for receiving the component from the transport head 20and then mounting the component onto the substrate; an imaging device orcamera 40 for imaging a position of the component held by the placementhead 30 immediately after the component has been transferred to theplacement head 30; a substrate holder 50 for holding and thenpositioning the substrate in place in the system 1; another imagingdevice or camera 60 for imaging a position of the substrate; and acontroller 70 for controlling the whole operation of the system 1.

[0033] Referring to FIGS. 1 and 2, the transport head 20 is supported bya horizontal guide (not shown) extending in the X-direction and isconnected with a motor 22 so that by the driving of the motor 22 thehead 20 moves back and forth in the X-direction. The placement head 30is also supported by a horizontal guide (not shown) extending in theX-direction and is connected with a motor 32 so that by the driving ofthe motor 32 the head 30 moves back and forth in the X-direction.

[0034] As can be seen clearly by the comparison of FIGS. 2 and 14, inthe component mounting system 1 of the present invention, the imagingcameras 40 and 60 are located in different positions. For example, theimaging camera 40 is mounted adjacent a transfer station where thetransport head 20 transfers the component to the placement head 30. Theimaging camera 60, on the other hand, is mounted on the rear side of andoutside a region where the placement head 30 travels in the X-directionso that the imaging camera 60 does not interfere with the placement head30.

[0035] Referring again to FIGS. 1 and 2, the component supply 10 has anupper table, i.e., X-table (not shown), for supporting the componentsand a lower table, i.e., Y-table (also not shown), for supporting theX-table. The tables are mounted so that the lower table moves back andforth in Y-direction relative to the system and the upper table movesback and forth in X-direction relative to the lower table. For thispurpose, the tables are drivingly connected with respective motors 13and 14, so that by the driving of the motors 13 and 14 the tables moveback and forth in X- and Y-directions independently, allowing adesignated component to take a predetermined pickup position.

[0036] The transport head 20 is supported by a horizontal guide (notshown) extending in the X-direction and is connected with a motor 22 sothat by the driving of the motor the head 20 moves back and forth in theX-direction. A motor 21 is mounted on the transport head 20 for turningthe picked component upside down, allowing the component to betransported for the placement head 30 in a condition where theconnecting portion of the component is faced down.

[0037] The placement head 30 is slidably supported by a horizontal guide(not shown) extending in the X-direction and is connected with a motor32 so that by the driving of the motor 32 the head 30 moves back andforth in the X-direction. A motor 33 is mounted on the placement head 30for rotating the component about the vertical Z-axis and therebyorienting the component in a predetermined direction. Another motor 34is provided in the placement head 30 for the vertical movement of acomponent holding part of the placement head 30.

[0038] The substrate holder 50, which is slidably supported by a guiderail (not shown) extending in the Y-direction, includes a motor 52 forits movement in the Y-directions along the guide rail. The imagingdevice 60, which is also slidably supported by a guide rail 60 aextending in the X-direction, has a motor 62 for its movement in theX-direction along the guide rail (not shown). As described above, thecomponent imaging device 40 is fixed in the system 1 at a position whereit can oppose the placement head 30.

[0039]FIG. 3 shows a positional relationship of various parts andstations (i.e., pickup station A, transfer station B, and mount stationC) in the system. As can be seen from the drawing, each componentsupported on the component supply 10 is picked up by the transport head20 at the pickup station A. The transport head 20 moves in theX-direction (from left to right in the drawing) to the transfer stationB where it turns upside down to overturn the component into a state inwhich the component can be mounted on the substrate from its above. Theoverturned component 11 is then transferred to the placement head 30.The placement head 30 with the component 11 moves to the placementstation C to mount the component 11 onto the predetermined position ofthe substrate 51.

[0040] In order to control the sequential operations without anytrouble, an imaging device or camera 12 is arranged at the pickupstation A. The imaging devices 40 and 60 are arranged at the transferand placement stations B and C, respectively. Also, the imaging devices12, 40, and 60 are connected to the controller 70 (see FIG. 1) so thatthe images captured by the imaging devices are transmitted to thecontroller 70, respectively. As already described above, the imagingdevice 60 is positioned on the rear side of the placement head 30 toavoid the interference between the imaging device 60 and the placementhead 30.

[0041] Referring next to FIGS. 4A to 4H, operations performed atrespective stations will be described in detail hereinafter. Thedrawings illustrate the operations performed at the stations A to C,when viewed in the Y-direction. As can be seen from the drawings, theoperations performed at the pickup station A are depicted in FIGS. 4Aand 4B, operations at the transfer station B are in FIGS. 4C to 4E, andoperations at the placement station C are in FIGS. 4F to 4H.

[0042] At the pickup station A, as best shown in FIG. 4A, each of thecomponents 11 supported by the component supply 10 is recognized by theimaging device 12 from above. By the use of the information transmittedfrom the imaging device 12, the controller 70 moves the component supply10 so that the component 11 to be picked up and then mounted on thesubstrate 51 takes the pickup position. Then, as shown in FIG. 4B, thetransport head 20 reaches above the pickup position and then movesdownward to pick up the component at the pickup position. Thereafter,the transport head 20 moves upward and then travels toward the transferstation B, i.e., from left to right in the drawing. At this moment, theimaging device 12 is located above the pass of the transport head 20 sothat no interference would be made between them.

[0043] Referring to FIG. 4C, at the transfer station B, the transporthead 20 turns upside down so that the component is oriented into aplacement condition. This allows that the electric connections such assolder bumps provided at a bottom surface of the component to bedirected downward for the mounting onto the substrate. Although thesolder bumps are widely used for the electrical connections between thecomponent and wires on the circuit board for the mounting of, forexample, an oscillator, the electrical connections can be performed bythe use of a conductive adhesive. Also in this placement condition, atop surface of the component, typically without any bump, is easy to bereceived or sucked by the vacuum nozzle of the placement head 30.

[0044] Although the turning operation of the transport head 20 isperformed at the transfer station B in this embodiment, it can be doneas the transport head 20 moves from the pickup station A to the transferstation B.

[0045] Also, although the transfer of the component is performedvertically from the transport head 20 to the placement head 30, it canbe done in any direction such as horizontally or obliquely.

[0046] At the transfer station B, the vacuum nozzle of the placementhead 30 moves down toward the transport head 20 positioned below theplacement head 30 to contact with and then suck the component 11.Simultaneously with this, the transport head 20 releases the component11, causing the component 11 to be transferred to the placement head 30.

[0047] After the transfer of the component 11, the transport head 20moves away from the transfer station B toward the pickup station A(i.e., from right to left in the drawing) for the subsequent pickupoperation of the component 11. As shown in FIG. 4E, the movement of thetransport head 20 away from the transfer station B allows the component11 held by the placement head 30 to fall within the field of the imagingdevice 40 located under the transfer station B. The imaging device 40recognizes the component 11 held by the placement head 30. The image ofthe component is then transmitted to the controller 70 by which theposition of the component 11, including X- and Y-lateral positions ofits center, angular orientation, is determined.

[0048] During the above operations performed at the pickup and transferstations A and B, the substrate 51 is transported from a substratesupply not shown into the placement station C and then held by thesubstrate holder 50. As shown in FIG. 4F, the substrate 51 is opposed tothe imaging device 60 for capturing the image of the substrate toidentify respective locations of indications marked on the substrate.For this purpose, as best shown in FIG. 4F, the substrate 51 as well asthe substrate holder 50 is moved from the placement station C to anoffset position, spaced rearward away from the station C. Mounted abovethe offset position is the imaging device 60 for picking up image of theindications. After the image pickup, the substrate holder 50 togetherwith the substrate 51 is carried back to the placement station C, asshown by the dotted lines in FIG. 4I.

[0049] It should be noted that the imaging device in the conventionalsystem is designed to move in two directions, i.e., X- and Y-directions,which requires two feed mechanisms. However, the imaging device 60 ofthe present invention moves back and forth only in the X-direction. Thismeans that one of the two feed mechanisms can be eliminated from thesystem, which is more economical and improves the quality of therecognition.

[0050] Also, according to the conventional system the imaging device isdesigned to move into the operational position in which it opposes thesubstrate. At this moment, in order to avoid the possible interferencebetween the imaging device and the placement head, the placement head aswell as the vacuum nozzle should be moved up and away from the imagingdevice. This requires another waiting time for the placement head, whichresults in the extension of the overall mounting time.

[0051] According to the present invention, the placement head 30occupies a certain region spaced away from that of the imaging device60, which ensures that no interference would occur between them. Thisalso allows the imaging device 60 to pick up images at any time,irrelevant to the position of the placement head 30, reducing themounting time.

[0052] The controller 70 determines a positional deviation between apredetermined sucking point and an actual sucking point by the nozzleand an angular orientation of the component, by the use of the image orsignals transmitted from the imaging device 40. Also, the controller 70determines a positional deviation between the predetermined and theactual positions of the indications on the substrate 51, by the use ofthe image or signals transmitted from the imaging device 60. Takingaccount of these deviations, the controller 70 calculates a travellingdistance to the placement station, a rotating angle of the nozzle 31about the vertical Z-axis, and a displacement of the substrate 51 withrespect to the Y-direction. Based upon the calculation, operations ofthe motors for moving the placement head 30 and the substrate 51 arecontrolled by the controller 70.

[0053] After the transfer and the recognition of the component at thetransfer station B, the placement head 30 begins to move toward theplacement station C (i.e., from left to right in the drawing). Also,after the correction of the positional deviation and the angularorientation by the controller 70, the placement head 30 moves to theplacement station C, as shown in FIG. 4G. Thereafter, as shown in FIG.4H the placement head 30 places the component 11 in place on thesubstrate 51.

[0054] In this operation, the nozzle 31 sucking and holding thecomponent moves down with the placement head 30 toward the substrate 51.Once the solder bumps provided on the bottom surface contact with thesubstrates 51, the placement head 30 forces the component 11 against thesubstrate 51. Simultaneously, the placement head 30 applies a highfrequency vibration to the component 11, causing the solder bumps to beconnected with the substrate. The vibration may be an ultrasonic wavegenerated by a piezoelectric device. For example, the ultrasonic wavehas an amplitude of about 1 micron and a frequency of about 63,000 perminute. After the completion of the component mounting, the placementhead 30 moves back to the transfer station B for the subsequent mountingof the component.

[0055] The imaging device 40 picks up the image of the placement head 30as the head is waiting for the next transfer operation to determine theexistence of debris. If the debris is detected, the system suspends thesubsequent operations for the removal of the debris, which wouldotherwise cause any damage to the component 11 or the nozzle 31. Thisoperation can equally be applied to the transport head 20. In thisinstance, the imaging device 40 picks up the image of the nozzle of thetransport head 20 to detect any debris on the nozzle. Preferably, thisis performed as the placement head 30 is moving toward the placementstation C. Further, at the placement station C, after the placementoperation by the placement head 30, the substrate 51 may move rearwardto a shifted position where it opposes the imaging device 60 for pickingup an image of the substrate 51 and thereby determining whether thecomponent 11 has been mounted in place on the substrate 51.

[0056] The imaging device 40 positioned at the transfer station B allowsthe component 11 to be recognized before the placement head 30 begins tomove toward the placement station C, which ensures the placement head 30to move continuously without any halt. The position of the imagingdevice 40 is not limited thereto. For example, the imaging device 40 maybe positioned in the vicinity of the transfer station B or in anotherposition spaced slightly away from the position where the component istransferred from the transport head 20 to the placement head 30. Thereason why the imaging device 40 is placed at or immediately adjacentthe transfer station is to avoid any loss of time which is caused in theconventional operation that requires the placement head needs to haltafter it has reached the maximum speed in the course of moving from thetransfer station to the placement station for the recognition of thecomponent and also the imaging device to wait until the vibration causedby the halt will come to an end. In this regard, the time loss can bereduced to some extent even when the placement head makes a halt beforeit reaches the maximum speed. Therefore, the terms “vicinity” and“spaced slightly” means a certain range in which the placement head isaccelerated up to the maximum speed.

[0057] Referring to FIGS. 5A and 5B, descriptions will be made to thisin details. As shown in FIG. 5A, according to the conventional system inwhich the placement head halts in the course of moving from the transferstation to the placement station for the recognition of the component bythe imaging device, a certain time of about 0.1 second is required fordamping the vibration of the placement head caused by the inertial forceof the placement head with a weight of about 10 kilograms, for example.After recognition, the placement head moves to the placement station,during which it is accelerated and then decelerated again.

[0058] Contrary to this, according to the mounting system of the presentinvention, as shown in FIG. 5B, after the transfer of the component, thetransport head 20 moves away from the field of the imaging device.Immediately after that, the component held by the placement head 30 isrecognized. Then, the placement head 30 accelerates to the maximumspeed, moves with the speed, and then decelerates to reach the placementstation. This eliminates the additional acceleration and decelerationrequired in the conventional system, which decreases the cycle time byabout 0.2 seconds.

[0059]FIG. 6 shows a relationship of movements and operations for theplacement head 30, transport head 20, and substrate holder 50. As can beseen from the drawing, after the placement of the component, theplacement head 30 moves back from the placement station C to thetransfer station B. In synchronism with this, the transport head 20which has already picked up the subsequent component moves from thepickup station A toward the transfer station B. The heads 20 and 30 haltto oppose each other at the transfer station B and then approach eachother for the transfer of the component from the transport head to theplacement head, which is illustrated by a hollow arrow directed upward.Immediately after the transfer of the component, the transport headmoves back toward the pickup station, allowing the recognition of thecomponent held on the placement head 30 by the use of the imagingdevice. The recognition operation of the component is illustrated as ahatched box. When the recognition is completed, the placement head 30moves toward the placement station C. During the movement of theplacement head 30, the recognition operation for the substrate 51 isperformed, which is illustrated as another hatched box. Then, thesubstrate holder 50 moves to the placement station C where the placementhead 30 places the component on the substrate 51, which is illustratedby a hollow arrow directed downward. During this, the transport head 20picks up the subsequent component from the component supply. Theabove-described operations are repeated for each component.

[0060] Provided below is a comparative table showing movement axes andmechanisms (i.e., feed mechanisms for X-, Y-, and/or Z-direction) forthe transfer and placement heads, the imaging devices, and the substrateholder, required for the conventional system and the system of thepresent invention. It should be noted that the increase of the number ofthe feed mechanisms complicates the structure of the system and alsodecreases the positional precision of the component and the devices suchas head and substrate. TABLE Feed Mech. Required Element System 1 System100 Improvement Head 20 X, Z X, Z Z-Displacement Reduced Head 30 X, Z X,Z Z-Displacement Reduced Device 40 X, Y — No X,Y-Feed Mech. [Y or Z] [NoX-Feed Mech.] Holder 50 Y Y — Device 60 X, Y X No Y-Feed Mech.X-Displacement Reduced

[0061] As can be seen from the table, the system according to thepresent invention, the fixed imaging device 40 does not need X- andY-feed mechanisms needed for the conventional system. This not onlysimplifies the structure of the system but also increases thepositioning and imaging precision. Meanwhile, the imaging device 40 maybe designed to move Y- or Z-direction, which will be described below.Even in this embodiment, one of the two mechanisms is eliminated. Thisis illustrated in the table by bracketing.

[0062] For the imaging device 60, only one (i.e., X-feed) mechanism isneeded. This means that one mechanism can be eliminated from theconventional system which needs two (X- and Y-) feed mechanisms. This isbecause the substrate 51 is shifted away from the placement station toanother position for its recognition by the imaging device 60. Thereduction of the feed mechanism also increases the recognition precisionof the substrate. Although the system is designed so that the substrateholder moves back and forth in Y-direction, it may be moved in anotherdirection provided that the substrate can be recognized by the imagingdevice in a certain position away from the placement station and theimaging device 60 does not make any conflict with the placement head 30.

[0063] Further the system of the present invention can shorten themoving passes of respective moving elements. For example, according tothe conventional system the vacuum nozzle 31 of the placement head 30 isrequired to move about 40 mm in the vertical direction in order to avoidthe interference with the imaging devices. Contrary to this, accordingto the system of the present invention, the imaging devices 40 and 60are located at difference positions and outside the passage of theplacement head 30 in the movements in the X-direction. This minimizesthe vertical movements of the nozzle 31 in the placement head 30 at thetransfer and placement stations down to about 1 mm, for example, whichis required for the prevention of the interference with the component.

[0064] Further, according to the conventional system, the imaging devicefor the substrate recognition is assembled with another imaging devicefor the component recognition. This requires both imaging devices tomove a long distance of about 250 mm, for example, between the componentand substrate recognition stations. However, according to the system ofthe present invention, the substrate recognition device is separatedfrom the other component recognition device so that it is served onlyfor the recognition of the substrate. Therefore, the substraterecognition device is required to move only a limited distance of about10 mm, for example, which might differ depending upon the size or thepurpose of the component. The reduction of the moving distance resultsin the reduction of the inertial force of the movement mechanism as wellas the necessary rigidity of the supporting structure and also in theincrease of the precision of the positioning.

[0065] As described above, the system 1 of the present invention has anumber of moving parts. Among other things, the placement head 30 movesabout 500 mm in the X-direction between the transfer and placementstations B and C. The movement of each element should be controlledprecisely in order to attain the precise alignment of the components onthe substrate. For this purpose, the system employs servomotors,pulse-motors, and/or voice-coil motors for controlling the movingdistance of the elements. In addition to those motors and in combinationtherewith, a linear scale may be used for each moving mechanism in orderto attain a more precise control of the moving distance. The linearscale, which is a pulse encoder for measuring a liner displacement, hasa reference scale with indices marked optically or magnetically and adetector mounted for movement on and relative to the reference scale,which ensures a precise movement control. Taking such feature intoaccount, the linear scale is preferably used for the compensation of thechange of moving distance that might be caused by heat.

[0066]FIG. 7 is a circuit diagram showing various parts incorporated inrespective devices described above. As can be seen from the drawing, thesystem has a hardware section and a software section. The hardwaresection includes the component supply 10, transport head 20, placementhead 30, component recognition device 40, substrate holder 50, andsubstrate recognition device 60. The software section includes variousprocessing units for controlling necessary operations for supplyingcomponent, sucking component, calculating an amount for positioncorrection, calculating an amount for angular correction, recognizingcomponent, recognizing reference-indication, and correcting position.The hardware and software elements are integrated with the controllerthat controls the overall operations of the elements.

[0067] Each of the hardware elements whose operations are alreadydescribed above has various drivers connected through respective linesextending out from the elements. The controller receives signals fromrespective units of the software section and, based on which, controlsrespective drivers. Among other things, the component supply processingunit controls the movement of the component supply 10 so that thecomponent to be picked up is placed at the pickup position. Thecomponent sucking processing unit controls timing and vacuum for thecomponent sucking by nozzles mounted on the transfer and placementheads. The units for calculating positional and angular correctionscalculates, from signals transmitted from the recognition device 40, amoving distance of the placement head 30 in the X-direction for themounting and the amount of angular correction for the nozzle 31 aboutthe vertical Z-axis. The component recognition unit controls therecognition timing by the recognition device 40 and the field of thedevice. The reference-indication recognition unit controls therecognition timing and the field of the substrate recognition device 60and, based upon the recognition by the device 60, the positioncorrection unit controls the moving distance of substrate holder 50 inthe Y-direction. With the arrangement, the recognition devices 40 and 60are separated from each other, which allows respective devices 40 and 60to be controlled independently, without any restriction imposed by theother device.

[0068] Referring to FIG. 8, another mounting system and method accordingto the second embodiment of the present invention will be describedhereinafter. The component mounting system of this embodiment, generallyindicated by reference numeral 2, is similar to that of the firstembodiment except that the system 2 has a second placement head 80.Therefore, like parts bears like reference numerals throughout thedrawings.

[0069] Meanwhile, according to the system of the first embodiment, theplacement head 30 receives the component at the transfer station B andthen moves to the placement station C for the mounting of the component.The mounting of the component at the placement station C is completed bythe ultrasonic connection, which needs a relatively extended period oftime of about 0.5 seconds. This increases a waiting time of associatedelement or elements, which results in an unwanted extension of theoverall time for mounting.

[0070] Contrary to this, in the system 2 of this embodiment, the firstand second placement heads bear respective functions and thereby enhancethe productivity of the mounting. For example, the system 2 is designedso that the placement head 30 serves for a first step of mounting inwhich the component 11 is mounted on the substrate 51 and then connectedtemporally by the ultrasonic vibration. The temporal connection requiresonly a limited time of about 0.1 second. After the temporal connection,the placement head 30 moves back from the placement station C to thetransfer station B where it receives the next component from thetransport head. The second placement head 80 serves for a second step ofmounting in which it applies the ultrasonic vibration again to thetemporally connected component 11 for the permanent connection of thecomponent to the substrate. The permanent connection requires anothertime of about 0.4 seconds.

[0071] With the two-step connection embodiment, the first (temporal) andsecond (permanent) connections by the placement heads 30 and 80 requireabout 0.1 and 0.4 seconds, respectively. Therefore, the total connectiontime appears to be identical to that required by the system 1 of thefirst embodiment. However, according to the system 2, after the temporalconnection, i.e., during the permanent connection, the placement head 30can proceed to receive the next component, which means that the overalltime for mounting per component is substantially reduced by, forexample, 0.4 seconds.

[0072] Therefore, the functional separation using two placement headscauses the overall time for mounting of the component to be reducedconsiderably and also the productivity of the system to be increasedsignificantly. Besides, the two-step connection provides a drasticincrease of the connecting force of the component than the one-stepconnection.

[0073] In order to provide the ultrasonic vibration to the componenteffectively, another holder in the form of bracket or box cover may beused for holding the component and then forcing it to the substrate.

[0074] Also, in the two-step connection, the position and/or orientationof component mounted temporally on the substrate may be recognized bythe recognition device and, if necessary, corrected at the permanentconnection base upon the recognition result. In this instance,immediately after the temporal connection of the component by theplacement head 30, the substrate 51 is transported rearward to opposethe fixed recognition device 60 for the recognition of the componentmounted temporally on the substrate. Then, based on the positionalinformation transmitted from the recognition device 60, the controller70 calculates the amount for X-, Y-, and/or angular correction and thencontrols the movement of the other placement head 80.

[0075] Preferably, the recognition device 40 recognizes the componentholding portion of the placement head 30 immediately after the temporalmounting of the component and the component holding portion of anotherplacement head 80 before the permanent mounting of the component. Thisallows the controller 70 to prevent any possible accidents, which may becaused by the existence of debris at the component holding portions ofthe placement heads. Also, this allows the placement head 80 to hold thetemporally mounted component positively.

[0076]FIGS. 9A to 9J schematically shows a series of operationsperformed at the pickup, transfer, and placement stations by the system2. As can be seen from the drawings, the operations illustrated in FIGS.9A to 9G are the same as those illustrated in and described withreference to FIGS. 4A to 4G.

[0077] According to the system 2 of this embodiment, in particular, thecomponent 11 is temporally mounted on and connected with the substrate51 as shown in FIG. 9H. After the completion of the temporal connectionof the component, the placement head 30 moves back in the X-direction tothe transfer station B for the transfer operation of the next component.After the disengagement with the placement head 30, the substrate 51moves rearward in the Y-direction to oppose the recognition device 60.As shown in FIG. 9I, the recognition device 60 recognizes the componenttemporally connected on the substrate 51 and then transmits therecognized image signal to the controller 70. The positionalrelationship between the substrate 51 and the recognition device 60 issimilar to that shown in FIG. 9K. After the recognition, the substrate51 moves back in the Y-direction to the placement station where itopposes the second placement head 80. As shown in FIG. 9J, the placementhead 80 moves downward to hold the temporally connected component 11.Also, the placement head 80 forces the component 11 to the substrate andthen provides the component with the ultrasonic vibration for thepermanent connection of the component to the substrate.

[0078] As best shown in FIG. 9J, the component holding portion of theplacement head 80 is defined in the form of bracket. Alternatively, theplacement head takes another configuration suitable for the positioningof the component and the application of the ultrasonic vibrations to thecomponent.

[0079] It should be noted that when any misalignment such as impropermounting or connection of the component is detected by the recognitiondevice 60 (see FIG. 9I), the controller 70 suspends the mountingoperation to make a warning. In this case, if necessary, the substrate51 may be discarded automatically or manually.

[0080] Referring to FIGS. 10A and 10B, another embodiment of the systemaccording to the present invention will be described hereinafter. Thedrawings illustrate positional relationships between the componentsucked and held by the nozzle 31 of the placement head 30 and therecognition devices in the conventional system (FIG. 10A) and the systemof the present invention (FIG. 10B), respectively.

[0081] As described above with reference to FIGS. 13 and 14, accordingto the conventional system the space between the component 111 a held bythe nozzle 131 of the placement head 130 and the substance 151 is solimited. This fails to ensure a distance, between the recognition device140 and the component, necessary for the proper recognition of thecomponent, which reduces the resolution of the image of, in particular,the large size component. Contrary to this, the recognition device 40 ismounted only for the recognition of the component and therefore fixed inthe system, which does not need additional space to avoid theinterference with the neighboring members. This in turn defines a largerspace between the recognition device 40 and the component than theconventional system, which increases the field and/or resolution of therecognition device 40. The increase of the field and resolution areillustrated by dotted lines α and long and short dotted lines β in FIG.10B

[0082] Improvement on the field and/or resolution of the recognitiondevice can be attained by another embodiments illustrated in FIGS. 11Ato 11F. For example, according to the embodiment in FIG. 11A, therecognition device 40 is designed to shift in the direction indicated byarrow 45, i.e., the X- or Y-direction, to a certain extent. With thearrangement, first the recognition device 40 occupies a first positionwhere it recognizes a part of the component. Then, the recognitiondevice 40 moves to a second position where it recognizes the remainingpart of the component. Partial images of the component are then combinedand processed at the controller for the subsequent processes such asposition and/or angular correction of the component. This process allowsthe recognition device to capture the entire image of the component witha necessary resolution even within a limited space. This in turn meansthat the moving range of the recognition device for the componentrecognition can be minimized. In addition, the horizontal movement ofthe recognition device 40 may reduce the likelihood that it suffers fromany damage by the possible drop of the component or other members.

[0083] Although the whole image of the component is captured through twopickup processes, more number of pickup processes can be employed forthe larger component.

[0084] In another embodiment in FIG. 11B, the recognition device 40 isdesigned to move vertically, i.e., in the Z-direction between a loweredposition indicated by solid lines and an elevated position indicated bydotted lines. This embodiment allows the recognition device 40 to shiftits focus vertically so that the components with different heights or atdifferent levels can be recognized without any defocus. For example, asshown in the drawing the larger component 11 is moved down from theelevated to the lowered position to extend its field, so that the entireimage of the larger component can be captured by one shot. Therecognition device 40, due to its movability in the vertical direction,is also available for the detection of debris carried by the componentholding portion of the transfer and placement heads 20 and 30.

[0085] In another embodiment in FIG. 11C, the recognition device 40 issupported by a horizontal axis not shown so that it rotates as indicatedby arrow 47. This arrangement allows the recognition device 40 to takebetween a first position (indicated by solid lines) where it recognizesa part of the component and a second position (indicated by dottedlines) where it recognizes the remaining part of the component. For thispurpose, the recognition device is connected with a driving source suchas pulse motor that is controlled by the controller. The system may bedesigned so that the recognition device takes three positions where therecognition device captures respective parts of the component.

[0086] In another embodiment in FIG. 11D, the recognition unit has twofixed recognition devices 40 a and 40 b in order to enlarge the field ofthe recognition unit. This arrangement allows the larger component to berecognized by two recognition devices with a high resolution. Also, thisarrangement may be used so that either one of the recognition devicesworks for a small component, and both for a large component. Of course,the number of the recognition is not limited to two.

[0087] In another embodiment in FIG. 11E, the recognition device 40 isoriented horizontally. Also, the recognition unit has a mirror 41. Themirror 41 is located in front of the recognition device 40 and supportedfor rotation so that the field of the recognition device is reflectedand then moved across the component. With this arrangement, the mirrorrotates between a first position where the reflected field of therecognition device covers a part of the component and a second positionwhere the reflected field covers the remaining part of the component.For this purpose, the mirror is drivingly connected to a motor, such aspulse motor, so that the controller controls the motor to rotate themirror. The mirror may be any member capable of changing a light pass,such as prism.

[0088] In another embodiment in FIG. 11F, the recognition unit has anoptical member 42 such as lens positioned between the recognition device40 and the component 11, allowing the recognition device 40 to pick upthe image of larger component. The optical member 42 may be supported tomove out of the space between the recognition device 40 and thecomponent 11. Two or more optical members may be prepared so that asuitable one of which is selected depending upon the size of thecomponent and/or the required resolution. Also, the optical member 42may be used in combination with other optical elements such as mirrorand prism. Further, the recognition device 40 may be supported formovement not only in this embodiment but also in the previous embodimentin FIG. 11E, which enlarges the field of the recognition device whilekeeping the required resolution.

[0089] While this invention has been described in conjunction with aspecific embodiment thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, it is intended to embrace all such alternatives,modifications, and variations that fall within the spirit and broadscope of the appended claims.

1. A component mounting apparatus, comprising: a component supplyprovided at a first station for supplying a component; a transport headfor picking up the component at the first station from the componentsupply and then transporting the component to a second station; aplacement head for receiving the component from the transport head atthe second station and then transporting the component to a thirdstation; a substrate holder provided at the third station for holding asubstrate, the substrate being provided with the component from theplacement head at the third station; and an imaging unit for recognizingthe component held by the placement head; wherein the imaging unit ispositioned in or in the vicinity of the second station.
 2. The componentmounting apparatus in accordance with claim 1, wherein the imaging unitis fixed in or in the vicinity of the second station.
 3. The componentmounting apparatus in accordance with claim 1, wherein the imaging unitis movable in a direction perpendicular to another direction along whichthe imaging unit opposes the placement head for the recognition of thecomponent.
 4. The component mounting apparatus in accordance with claim1, wherein the imaging unit is movable in a direction along which theimaging unit opposes the placement head for the recognition of thecomponent.
 5. The component mounting apparatus in accordance with claim1, wherein the vicinity is defined by a range in which the placementhead is accelerated up to the maximum speed in the course of themovement thereof from the second station toward the third station. 6.The component mounting apparatus in accordance with claim 1, wherein thetransport head turns the component upside down after receiving thecomponent at the first station and before transferring the component atthe second station.
 7. The component mounting apparatus in accordancewith claim 1, wherein the imaging unit is supported so that itrecognizes different portions of the component.
 8. The componentmounting apparatus in accordance with claim 1, wherein the imaging unithas a plurality of imaging devices.
 9. The component mounting apparatusin accordance with claim 1, wherein the imaging unit has an opticalmember for changing an optical feature of the first imaging unit. 10.The component mounting apparatus in accordance with claim 9, wherein theoptical member is a mirror, prism, or lens, or a combination thereof.11. The component mounting apparatus in accordance with claim 1, whereinthe imaging unit recognizes a portion of the transport head and/or aportion of the placement head, for holding the component.
 12. Acomponent mounting apparatus, comprising: a component supply provided ata first station for supplying a component; a transport head for pickingup the component at the first station from the component supply and thentransporting the component to a second station; a placement head forreceiving the component from the transport head at the second stationand then transporting the component to a third station; a substrateholder for holding a substrate, the substrate holder be movable betweenthe third station and a fourth station spaced a certain distance awayfrom the third station; a first imaging unit for recognizing thecomponent held by the placement head; and a second imaging unitpositioned at the fourth station for recognizing the substrate.
 13. Thecomponent mounting apparatus in accordance with claim 12, wherein thesecond imaging unit is movable in a first direction along which theplacement head moves between the second and third stations, and thesubstrate holder is movable in a second direction perpendicular to thefirst direction.
 14. The component mounting apparatus in accordance withclaim 13, further comprising a fixing head, so that the placement headmakes a temporal connection of the component to the substrate and thenthe fixing head makes a permanent connection of the component to thesubstrate.
 15. The component mounting apparatus in accordance with claim14, wherein the second imaging unit recognizes the component on thesubstrate after the temporal connection and before the permanentconnection of the component.
 16. The component mounting apparatus inaccordance with claim 14, wherein the second imaging unit recognizesportions of the placement head and the fixing head for holding thecomponent.
 17. The component mounting apparatus in accordance with claim16, further comprising a linear scale mounted on a shaft for guiding theplacement head between the second and third stations.
 18. A componentmounting apparatus, comprising: a component supply provided at a firststation for supplying a component; a transport head for picking up thecomponent at the first station from the component supply and thentransporting the component to a second station; a placement head forreceiving the component from the transport head at the second stationand then transporting the component to a third station; a substrateholder provided at the third station for holding a substrate, thesubstrate being provided with the component from the placement head atthe third station; a first imaging unit for recognizing the componentheld by the placement head; and a second imaging unit for recognizingthe substrate; wherein the first and second imaging units are arrangednot to interfere with a passage of the placement head.
 19. A componentmounting method, comprising the steps of: picking up a component by atransport head from a component supply at a first station; transportingthe component from the first station to a second station by thetransport head; transferring the component from the transport head to aplacement head at the second station; recognizing the component receivedby the placement head at or in the vicinity of the second station;transporting the component from the second station to a third station bythe placement head; placing the component onto a substrate at the thirdstation by the placement head; and controlling the step of placing thecomponent onto the substrate based upon information obtained by therecognition of the component.
 20. A component mounting method inaccordance with claim 19, wherein the vicinity is defined by a range inwhich the placement head is accelerated up to the maximum speed in thecourse of the movement thereof from the second station toward the thirdstation.
 21. A component mounting method in accordance with claim 19,further comprising a step of making a permanent connection of thecomponent to the substrate at the third station by a fixing head, afterthe step of placing the component onto the substrate by the placementhead.